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Hi Andy,
It is perhaps also interesting for spectroscopy. I see from the specs that the sensor is larger than the one in the SeeStar 30 which means that unlike the Seestars it could potentially be used directly with a Star Analyser recording the full spectrum in one shot (not including the zero order, though that plus the blue end of the spectrum could be captures separately.) The equatorial mode would also avoid the problem of the spectrum fanning out due to field rotation which is seen with the SeeStar. The tiny 2 micron pixels means the image is probably well over sampled which should be good for avoiding artifacts with the colour sensor.
Cheers
RobinThe specs on line say it has an (impressively large) 9.6v 45Ah internal battery, good for 10 hours operation
I suspect 45Ah may be a typo and the battery is actually 4.5Ah even though the 45Ah figure appears everywhere on different sites.
Compare for example with the effectively identical Celestron branded version, here where a space has been used instead of the decimal point (9 5v 4 5Ah)
https://altairastro.com/celestron-nexstar-evolution-925×22-sct-6537-p.asp
That would be ok for the claimed 10 hrs just tracking (at ~0.5A) but a lot of slewing would take more power. What life do you typically get with the internal battery ? (If the internal battery is 4.5Ah then say 3 x that time with the 17Ahr power tank would seem reasonable given that you don’t want to run down lead acid batteries too low to prolong their life)Cheers
RobinThe specs on line say it has an (impressively large) 9.6v 45Ah internal battery, good for 10 hours operation eg
https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/sky-watcher-fusion-120i-synscan-mount-and-tripod.html
so if that is correct, a 17Ah external power pack is not going to increase the run time dramatically. How long do you want to run for?Cheers
RobinI did a thing for the BBC news 6 & 10pm yesterday where they wanted a live image of a planet
Yes ! Heard your name , looked up from the observatory computer screen and saw a live image Of Jupiter on the 10 o’clock news. Was that a live feed? That has to be some kind of first hasn’t it ?
Ken,
Dark, bias flat and sky background subtraction (based on an interpolation using regions above and below the spectrum) is normally all handled by the spectrum reduction program
Cheers
RobinNot sure where the discrepancy arises but the minimum will be somewhat resolution dependent if the line is not fully resolved.
OK so the difference between my measurement and the BASS2000 spectrum is not just due to a difference in resolution. See attached comparison where the BASS2000 spectrum has been spline filtered to ~ match the resolution in my spectrum. The discrepancy is still there and looks to be due to a zero offset so I need to check back on how I did the background subtraction.
Attachments:
The very high resolution BASS2000 solar spectrum however has a minimum of ~0.15 at H beta
https://bass2000.obspm.fr/solar_spect.php
Not sure where the discrepancy arises but the minimum will be somewhat resolution dependent if the line is not fully resolved. EW would be a better measure of intensityCheers
Robinthere is a discrepency at Hbeta (min intensity ~ 0.2 compared to my value of ~ 0.35) which I would like to resolve.
Ken,
My measurement originally posted by Andy confirms your value of ~0.35 minimum for H beta as measured at R~18000
https://britastro.org/specdb/data_graph.php?obs_id=9871Cheers
Robinas well as downscaling, converting to video also involves significant compression with resulting artifacts and loss of detail, akin to using jpeg images
The amount of compression (in addition to the downscaling (binning by interpolation) can be seen by comparing the video size with the expected size of uncompressed frames. For example one minute of uncompressed 8 bit 1270×720 video at 60fps should be 1270*720*60*60 = ~3.3GB !
Cheers
RobinI forgot to mention that as well as downscaling, converting to video also involves significant compression with resulting artifacts and loss of detail, akin to using jpeg images so the resulting video is not like uncompressed avi from webcams (or ser from astro cameras) so RAW stills would be better. The downside is planetary imagers take hundreds or even thousands of frames to select the ones with good seeing to stack which would be impractical with RAW frames from a DSLR
Cheers
RobinSadly eclipse day was cloudy, but Gigglewick got it!
As a girl of 7, my mother lived in rural Lancashire a few miles along the track from Giggleswick and recalled the 1927 eclipse. She remembered the chickens rushing back into the hen house thinking night had fallen !
Not wishing to get people’s hopes up, but this interesting ATel #17041 was released just a few moments ago.
The spectrum from the ARAS database showing the increase in H alpha emission taken on 7th of February that they refer to is mine, though I have no connection with the team. (If this was my ATel I would definitely be putting a question mark at the end of the title !)
There are actually high resolution H alpha spectra close to all three dates in ARAS database
https://aras-databas…abase/tcrb.htm
See attached. Mine showing the increase in emission is in black.I am sceptical about any predictions of TCrB base on accretion rate though which varies continuously in all timescales. For example attached is a spectrum in the ARAS database from from Francois Teyssier taken in 2021 when it was in a continuous high state which shows the same H alpha intensity as my Feb 7th spectrum. Of course then again it might blow tonight ! We do urgently need more spectra though and unfortunately I have been clouded out since.
Cheers
RobinWe do have a spectrum of Europa in the BAA database, but it is low resolution with an R value of 564.
That link actually points to a high resolution solar spectrum by me (taken through a solar filter, not of the sky) though unfortunately although it covers H beta it does not cover Na D
Cheers
RobinIn the case of 640×480 video where the aspect ratio is lower than that of the sensor I would expect the downsampling to be done based on the height of the sensor and then the left and right edges cropped to match the aspect ratio ie 5184×3456 is downsampled to 720×480 and then cropped by 40 pixels left and right
Hi James,
Not the same camera but with my compact camera the video is downsampled from the native sensor resolution to the video resolution based on the width of the video frame and then if the aspect ratio of the video is different from that of the sensor, the video image is cropped in height. eg 5184×3456 would be downsampled to 1920×1280 and then cropped 100 pixels top and bottom to give 1920×1080. The downsampling ratio is not in general a whole number of pixels (ie a simple binning) so presumably it is done using some kind of interpolation algorithm to maintain image quality.
Cheers
RobinAn AAS research note has been issued discussing the similar short term flare event seen in amateur spectroscopic observations during November 2024
https://iopscience.iop.org/article/10.3847/2515-5172/adb425
(It is possible that these are common during the low state but may not be picked up due to observing cadence)Cheers
RobinThe Variable Star Section is a good example of why it can be useful to make a Circular public. I know that professional astronomers read it. If it were behind a pay wall then that might not happen. Having the professional researchers read the Circular benefits the members who contribute to the Section.
I’ve experienced this just today. It was an unexpected treat to see in a paper just published on the RW Cep “Great Dimming”
“Atmospheric dynamics of the hypergiant RW Cep during the Great Dimming”
https://arxiv.org/abs/2501.11701
several references to my BAAVSSC article on thisCheers
RobinAnd another paper
“Bridging the Gap: OPTICAM Reveals the Hidden Spin of the WZ Sge Star GOTO 065054.49+593624.51”
https://arxiv.org/abs/2501.11669
(Detection of a 148s periodic signal in high cadence photometry)Chrome win 10 here. I stay logged in to the BAA site if I close the tab but keep the browser open but it logs me out immediately when the browser is closed. Many websites/forums give the choice to be remembered or not (which IMO is the best arrangement) while with others (like Amazon for example and soon Outlook) you have to physically sign out unless you are using private browsing.
